It is human nature, especially in these times of frequently acclaimed scientific advancement, to expect to uncover all we wish to know.
With Covid-19, the list of what we don't know remains infuriatingly long. Why do some people get sick, and some don't? What's the long-term health impact of infection? How long will vaccine immunity last? And when will the pandemic end?
A South Auckland family who tested positive in August last year still do not know for certain, nor do we, how the virus emerged. Three potential sources have been suggested: a border incursion from overseas, namely from the UK or Ecuador; undetected community transmission; or the virus arriving via foreign goods.
There was speculation a September cluster originating from the Christchurch Crowne Plaza Hotel, which infected six people, started from a rubbish bin touched by a returnee at the facility.
Then there was the mystery November transmission from a member of the Defence Force working at an Auckland quarantine facility to a shop assistant who lived, worked and studied in the CBD.
Two Defence staff were traced to the Auckland CBD, spending two hours at a bar 100m from the woman's work on High St. But that's as close as the tracing got.
In January, a Northland woman tested positive for the virus after leaving managed isolation. She visited 30 southern Northland locations, including cafes, restaurants, retail outlets, tourist attractions and holiday hotspot Mangawhai. However, all 16 close contacts she encountered while travelling tested negative.
Phenomenally, perhaps, everyone she came into contact with tested negative.
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Later in the month, two people from the same MIQ facility also tested positive after leaving. Officials had no choice but the close the facility for a complete review. It reopened with improved ventilation, although links between the cases could only be theorised on.
The Valentine's Day cluster in February also left questions. Fifteen positive cases were eventually tracked back to a person who worked at a catering and laundry service in Auckland International Airport. How this person was infected is still unknown and listed as "under investigation".
The case of an airport worker who apparently picked up the virus while cleaning a plane that landed on April 10 has also never been solved. The cleaner was wearing full PPE, including an N95 mask, and there was no face-to-face contact with passengers.
In many of these cases, we know the virus has somehow passed from case to case because genome sequencing confirms it is the same variant, down to a minute level of detail.
In some cases, the chain of events and clearly trackable movements of people makes it clear that missing links must exist. The only reasonable conclusion is people carried the virus from one place to another but escaped detection and therefore, most likely, symptoms. This is as confounding as it is alarming.
Despite our great science and our desire to understand, it is humbling to realise there are some things we may never know. It's also a good reminder to avoid complacency - this pandemic hasn't finished yet, nor with throwing up surprises.